WHAT’S UP DOC? Polio-like illness

Tuesday

Nov 27, 2018 at 2:51 PMNov 27, 2018 at 9:29 PM

Q: This new polio-like illness has been in the news a lot lately.Can you help me understand what this is all about?

A: Poliomyelitis is caused by a virus that is shed in the stool of infected people (during acute epidemics it may be spread from pharyngeal secretions).Poor sanitary conditions and poor hygiene contribute to its spread.After infection, the virus replicates in the nose/throat mucosa and/or the gastrointestinal (GI) tract of the patient.It then invades the lymph nodes and possibly spreads to the blood; in some cases it can also invade the neurons in the patient’s brain and/or spinal cord.

About 90 percent of those infected with the polio virus have minor non-specific symptoms such as low-grade fevers, malaise, sore throat and/or headache, and these people recover with no sequelae.Some people also have GI symptoms such as nausea, vomiting and/or abdominal pain, and again typically have a full recovery.About one percent of those infected develop paralytic polio (damage to muscle innervating neurons), causing muscle weakness (most often in one limb or on one side of the body) which can progress to flaccidity (decreased muscle tone) and paralysis. Although there is no cure for paralytic polio, about half of the small percentage of patients that develop this condition recover fully on their own, a quarter have mild residual weakness and about a quarter have severe permanent disability.Overall, the prognosis is better for younger children. Polio infection is definitively diagnosed by cultures of certain body fluids or blood antibody tests.

Acute flaccid myelitis’ (AFM’s) characteristic features include an acute febrile illness, usually with upper respiratory symptoms (like a typical cold), which progresses to include neurological symptoms such as limb weakness and/or other nerve involvement (causing facial, eye, swallowing or speaking muscle weakness).There is not yet any specific test for AFM, although MRI imaging typically shows evidence of spinal cord gray matter involvement. Blood and other tests are usually done to evaluate for other possible causes of the symptoms.Therefore, AFM is diagnosed by identification of the flaccid limb weakness symptoms and the MRI findings, as well as ruling out other possible causes.

The rapid onset of flaccid weakness of AFM in one or more limbs is similar to symptoms from paralytic polio, and so has been described as “polio-like.”However, the underlying pathophysiology of AFM is not (yet) well understood.It is thought to be caused by a virus, and there are some specific suspect viruses; enterovirus D68 is a leading candidate (there are many types of enterovirus, causing over 10 million infections in the U.S. every year, usually just ‘common colds’).The incomplete understanding of AFM limits the ability to make a specific diagnosis and to confidently identify the mode(s) of transmission, as well as preventing development of preventive measures (such as a vaccine) or treatment.

These limitations, and the overall rareness of the condition (it is estimated to have caused severe symptoms in less than one per million Americans), make tracking the disease difficult.Despite this, the Centers for Disease Control has been following outbreaks of the disease and has noted 80 confirmed cases in 26 different states so far in 2018, with several hundred other cases (in 11 additional states) noted to be suspicious for AFM (there were outbreaks of AFM in 2014 and 2016, although the 2018 outbreak has been the largest so far).There have already been multiple deaths from this condition.

Despite the present limited understanding of AFM, there are some things that are known about this illness.AFM seems to most commonly cause symptoms in young children (most often less than 4 years of age).Its occurrence seems to peak in late summer/early fall (July through November).Almost two thirds of patients diagnosed with this illness do not regain full strength.The overall mortality from this condition is not yet known.

Anyone who develops acute weakness of a limb, facial/eye/swallowing/speaking or any other muscles should seek immediate medical care.There are many possible causes of these symptoms (for example several infectious diseases including polio, certain autoimmune diseases, strokes and may others), and evaluation to identify possible causes to help guide treatment and care is indicated. The CDC is working hard to better understand AFM, and with better understanding there may be hope for development of treatment and prevention (such as a vaccine as exists for polio).